Coronary artery calcification (CAC) is a leading biomarker for predicting atherosclerotic heart disease. CAC is a more accurate predictor of cardiovascular risk than cholesterol and other lipids. CAC is also more accurate than C-reactive protein and carotid intima media thickness measured from ultrasound or magnetic resonance imaging (MRI) as a predictor of cardiovascular risk. CAC score reclassifies approximately 50% of intermediate-risk individuals to high or low risk categories, where there are established treatment strategies. Thus, CAC is a useful biomarker of cardiovascular disease and may be used to trigger drug therapy, lifestyle changes, or additional testing of cardiovascular health. Educating patients as to their risks related to atherosclerotic heart disease can improve adherence to drug therapies and lifestyle changes including smoking cessation, dietary changes, and weight loss. Adding a computed tomography (CT) coronary calcium score as a risk factor improves the ability to predict a cardiac event in a population of persons with no known cardiac disease. Showing patients their CT coronary calcium images and discussing CAC scores may improve adherence to statin drug therapy in high risk groups compared to treatment approaches without such an intervention.
In addition to screening, CAC scores derived from CT imaging may be used to determine next steps in therapy. The relative risk of obstructive angiographic coronary artery disease (CAD) is higher for coronary calcium scores (4.53) than either treadmill-electrocardiogram (ECG) (1.72) or technetium-stress (1.96). The accuracy of coronary calcium is also significantly higher (80%) than alternative approaches to predicting CAD in a patient, including treadmill testing (71%) and technetium-stress (74%). Thus, CAC scores derived from CT imaging have been used to guide a physician in determining what therapies to apply to a patient.
CT coronary calcium scoring is also used in the National Institute for Health and Care Excellence (NICE) practice guidelines as a gatekeeper in the CAD diagnostic pathway. Patients classified with a low likelihood of CAD with a modified Diamond-Forrester (DF) score in the range of 10% to 30% are scanned for CT coronary calcium. A zero calcium score rules out additional cardiovascular imaging, including non-invasive or invasive coronary angiograms. Additionally, CT coronary calcium scoring is a useful indicator for statin therapy. However, the high cost and high radiation dosage of CT imaging limits the utility of conventional CT-based CAC scoring as a screening tool for CAD.